Individual differences in drug abuse vulnerabilities among humans are likely to display genetic as well as environmental components. During this year, these investigators continued to explore possible roles of allelic variants at candidate gene loci in possibly contributing to human individual differences in drug abuse vulnerability, published the first report of genome scanning approaches to identifying previously-unanticipated gene loci conferring drug abuse vulnerabilities and continued to make major advances in providing simulations and modeling for the power of genome-wide and focused association/linkage-disequilibrium based genome scanning. Work during this year provided replication and extension of identificaiton of candidate regions on several human chromosomes using high-density SNP and SSLP-based linkage-disequilibrium based genome scanning. Data is consistent with the emerging models that genetic influences are polygenic, with few major gene influences. Chromosome 7 regions previously nomninated in alcoholism studies may also play roles in polysubstance abuse vulnerability, with particular haplotypes at the NrCAM locus providing major roles.